Mycoplasma hominis is becoming recognized as a human pathogen. It can be detected in a variety of body sites and has an impact in both adult and pediatric populations. Currently there is no diagnostic test available. M. hominis is difficult to cultivate and requires serological identification which is time consuming and costly. We propose to develop an antigen detection assay for M. hominis by identifying M. hominis proteins which are common to all strains, produced in vivo, and are antigenically identical. Since the original submission of this grant, proteins in four molecular weight areas have been identified by one dimensional PAGE which fit these criteria. These proteins (and others) will be identified by two-dimensional gel electrophoresis (2-D page) and immunoblotting and the candidate proteins checked for cross- reaction with antisera against other mycoplasma species by the same techniques. Monospecific antisera will be produced to the candidate proteins (isolated from 2-D PAGE gels) which do not cross-react. These antisera will be tested for reactivity (using spot blots) with other organisms to assure specificity and with multiple M. hominis strains to verify commonality. These monospecific antisera plus a battery of monoclonal antibodies to be produced in Phase II will be the reagents used to develop an antigen detection assay.